Radiator tube end



April 1944- H. R. HEAVENER I 2,346,376

RADIATOR TUBE END Filed Aug. 17, 1942 PatentedjApr. 11; 1944 2,346,376 RADIATORYTYUBE END Harvey R. Heavener, Lockport, N. Y., assignor to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Application August 17, 1942, Serial No. 455,085

'2 Claims; (Cl. 153-2) This invention relates to annimprovement in the manufacture of thin walled tubes and more particularly to the production of expanded hexagonal ended tubes.

ning with a tool of the kind referred to is that scrap, is reduced to a negligible quantity. Production of good tubes is stepped up to between ninety-five per cent and one hundred per cent of the tubes produced and this means a decided A well known type of heat exchanger consists 5 saving in material and operation and of more of a bundle of tubes formed. of copper orother importance at the moment it means getting out similar material, with each tube having at oppo- .essential production fast. It makes more feasible site ends enlarged polygonal portions to be fitted the use of thinner wall stock which is easier and and bonded to complemental portions of neighless expensive to work and which enables a wanted boring tubes. Wall thickness must be kept small 1 weight reduction and a conservation of the supply for rapid heat transfer and thinness is of special of vital metals. importance in the interests of light weight for For a better explanation reference will be made aircraft installation. The lighter and thinner the to the accompanying drawing wherein Figure 1 is wall the more will be the difliculty experienced in a side elevation of a machine suitable for the forming and handling the tubes during manul sp p r i n; Fi ure 2 shows a tube end in facture, section and the working terminal of a spinner In manufacture the tubes are formed by an prior to the start of the enlarging oper ti extrusion process and the metal grain tends to ure 3 shows the same parts in operative relation; run in an axial direction. It has been the custom F gure 4 is a transverse Se through t e tavheretofore and a'fte'rkthe extrudedtube is cut to pered p i n f the or ng tool taken on line proper length, flrst to enlarge the end-portion by f Figure i ure 5 is a sectional view a direct, thrust from a round tool plunged axially showing parts suitable for the hexing operation; into the tube end'and then to transfer the tube Figure 6 is a detail section taken on line E6 of tot-another -machinein which the previously Figure 5 d Figures 8 and 9 are co p ion stretched'and. enlarged cylindrical end receives a iews o tube e ds W th Figure 7 indicating the boxing plunger whereby the cylindrical shape is grain direction in a tube spun to cylindrical excontor ted to apolygonal contour consisting of a B n ed pe before th flexingv Operation; circumferential succession of flat sided lands with ure 8 showing the same tube after the hexing opsharp corners therebetween on axial lines of bendoration and Figure .9 showing a completed tube ing. 'Iihis procedure involves avery great propormade according to previous practices and wheretion of split tubes because in hexing the ends, in the grain direction is parallel to the lines of many of the tubes split and the scrapped tubes bending. amount to as much as from one-third to one- It will be understood that any suitable type of f; total producei machine may be employed for performing the Instead of expanding the tube ends by a direct spinning operation and that merely for 11 t thrust it is 'now proposed to effect enlargemen ve purposes there is shown in Figure 1 a maby a spinning operatioriand for this purpose a chine comprising a bed I having fixed at one end special spinningv tool is employed having a frustoa housing 2 containing drive mechanism for a conical work performing portion which is fed into chuck 3 and having adjustable on the bed a holder the tube end and on which are formed a series of 40 4 including a chu k One-of the chucks will be spaced indentations. It is thought that the shalemployed to mount the shank of the spinning low fluteshincorporate into the expanding action tool and the other chuck will hold the tube to of the spinning enlarger, a sort of hammer effect be expanded and the tube and the t l win b and twists the wall. While it cannot be stated brought into engagement and fed forward by exactly, it seems that the metal having been proper manipulation of the traveling carriage 4 twisted or torsionally deformed during the spinwhile relative spinning torsion will be imparted ing operation, has its grain direction bent or to th parts by the mechanism contained in the pulled over to follow a spiral path and that in the housing 2. Obviously, the machine may be consubsequent insertion of the hexing tool the metal structed so that a pair of expanders move in tomerely. folds over the corners of the tool insteadJSO ward one another to expand Opposite tub ends of tearing straight down on lines parallel to axial in a single operation with relativespinning rotagrain direction as appears to be the case heretotion between the tube and the pair of tools. mm One end of the expander tool is constituted The practical result with this operation of spiny the mounting shank 6 and the opposite end is constituted by a reduced terminal or pilot 1 the shank 6 and determines the final expanded diameter of the tube end. The longitudinally tapered portion 9 has formed inits wprking surface a series of circumferentially spaced axially extending depressions or flutes II which break the circular continuity of the tapered periphery. These formations may be made by milling flats at predetermined locations in the tapered surface of the tool. 4 I f In the tube expanding operation to enlarged cylindrical cross section, the forming tool and the tube are held by the chucks in coaxial relation and as one of the chucks is spun or rotated at a rapid rate the pilot I is caused to enter the tube end and as the parts are fed together the tapered portion 9 comes into engagement with the tube end and wedges or stretches its diameter to that of the collar [0. In the relative spinning action, the tube wall evidently tends to conform to the peripheral outline of the work performing surface of the tool and as the wall is stretched it bridges the flats H, or, in other words, it follows th hills and valleys presented by the succeeding circular lands and ilats'and draws in and out of the depressions, so that the leading edges of the circular lands hammer the wall or perhaps more properly speaking dig and scrape against'the wall surface as the wall and tool surfaces sweep or scuff over one another with a frictional drag. At any rate a torsional force, incidentto spinning, is imposed on the wall and as the spinner progresses into the tube, the wall continues to be twisted and eventually the lines of grain direction become spiraled at completion of the operation, some- I what in the fashion illustrated in Figure 7.

Any suitable device for effecting the hexing operation may be employed and merely by way of example there is illustrated in Figure 5, a holder l2 for the central portion of the tube and a die l3 to receive the cylindrical tube end enlargement. A hexing plunger l4 upon insertion intothe tube end will conform the tube to the desired polygonal cross section. The bending in the tube wall from cylindrical to flat sided outline and especially at the sharp corners will all occur on axial lines which in the case of a twisted tube will traverse or be out of parallel with the lines of grain direction. This is illustrated in Figure 8 and is believed to explain why slitting of the tubes is reduced to a minimum. By contrast it will be noted that when the lines of grain direction are parallel to the lines of bending, as seen in Figure 9, the likelihood of splitting under the contorting stress applied is more pronounced than it is with the out of parallel relation between the lines of grain direction and the lines of bending.

travel crossingithe lines of wall twist.

2. The method of making polygonal ended tubes including stretching to enlarged diameter and twisting the end portion of the tube wall and then inserting axially therein a polygonal shaper having its apices between its flats projecting on axial lines across the lines of twist.

3. The method of forming polygonal shapes on tubes which initially have grain direction extending axially of the tubes, including contorting the tube wall to change its grain direction and then plunging a polygonal forming tool into the tube in the axial direction so that the axially extending corners of the tool traverse the direction of grain in the tube wall. v

4. The method of forming to'polygonal shape a cylindrical wall whose grain direction initiallyis substantially parallel tothe cylinder axis,-including working the wall to reform the course of grain direction to non-parallel relation with the cylinder axis and thereafter deflecting the wall to polygonal shape on substantially axially extending ;lines transverse to the reformedcourse of rain direction. 5 I

5. The method of working'tube ends to polygonalshape, including introducing an expander having a working periphery'of non-circular-outline into the tube end and simultaneously therewith causing relative-spinning motion between the tube and expander for dragging the wall tor- :sionally as its diameter swells, and thereafter axially plunging a shaper 'of polygonal cross section into the expanded and twisted-tube en'd.

6. Themethod of Working atube end'to enlarged polygonal cross section, including causing relative spinning motion between-a tube and an expander tool whose tube engaging land is circumferentially discontinuous and sweeps over the .tube wall to stretch and also-impose a twisting the wall of the tube endto stretch the same to enlarged diameter and torsionally twist the lines of graintherein and then deforming theexpanded tube wall from cylindrical to polygonal cross section on lines of bending which traverse said grain lines.

HARVEY R. HEAVENER. 

